I don't live in "planet USA", in fact, I live in Argentina, but I still care about english and correct spelling. Wrong spelling doesn't look very nice. How is correcting mistakes immature? It's the other way around, immature (young) people are the ones who tend to make those mistakes. How is correcting mistakes dumb? It's the other way around, dumb people are the ones who tend to make those mistakes. And about the impolite part, well, I guess it's true, but falsely accusing a legit site of scam (which is a pretty strong accusation) is also impolite.

Also I wanted to point out that you can't "criticize" spelling/grammar, as they are objective and not subjective, so there's a correct way and an incorrect one.